This invention relates in general to apparatus for monitoring the status of many-cell storage battery systems and, in particular, to a system for automatically sensing a plurality of parameters of each cell, coupling the data to a remote location, providing an alarm when a cell parameter is not within preselected limits, and displaying the parameters of a selected cell.
Accurate and reliable information about the battery status is required in cases where high-capacity, many-cell battery systems provide operating or emergency power. The lead-acid storage battery system of a submarine is such a case. In these systems, it is desirable to monitor the cell parameters such as operating voltage, operating temperature, electrolyte level, electrolyte specific gravity, and electrolyte level, electrolyte specific gravity, and electrolyte circulation since these parameters indicate problems or potential problems in battery performance.
For example, a higher than normal operating temperature in a cell may indicate an internal short circuit or excessive resistance within intercell connections or internal to the cell. A higher than normal temperature will increase capacitance, local losses, and charging current for a given voltage and, in general, will shorten the life of the battery. If the electrolyte level of the cell drops so low as to expose the surface of the cell electrodes, the cell may be quickly and permanently damaged. On the other hand, if a cell is overwatered prior to charging, the electrolyte may overflow during or following charging with deleterious consequences. It is also desirable to monitor the state of charge in a lead-acid storage cell. One measure of the state of charge (and thus a measure of the cell's condition) is the concentration of sulfuric acid in the cell electrolyte. In large, lead-acid storage cells it is necessary to mechanically circulate the electrolyte to prevent the acid from settling to the bottom, thereby causing the electrolyte to have a non-uniform concentration. Usually an air-lift pump is used to circulate the electrolyte. Since a non-uniform concentration of electrolyte will adversely affect cell longevity, it is desirable to monitor the flow from the lift pump and thus obtain a measure of the circulation of the electrolyte. Depending on the battery system it may be desirable to monitor cell characteristics in addition to or instead of the ones just noted.
Typically, the foregoing parameters have been monitored in the large, many-cell battery systems by visual inspection or manual measurement of the parameters in randomly selected cells. The electrolyte temperature has been usually measured by opening a few random cells and inserting an alcohol thermometer; the state of charge has been inferred from hydrometer readings taken in a similar manner; the electrolyte level has been measured by inserting a glass or plastic tube; the electrolyte circulation has been monitored by observing the total air flow to banks or many cells; and the cell voltage has been monitored by connecting wires to the cell terminals and thence to a remote monitoring location.
In addition to inaccuracies inherent in the manual measurements, the foregoing approach is of limited effectiveness in detecting problems and is also time-consuming. Often the batteries are located in inaccessible areas further complicating the manual monitoring of the battery parameters. Monitoring only a randomly selected portion of the cells has obvious limitations in detecting potential problems and obtaining an accurate knowledge or system operability.